All-Blue Potatoes This page first published: Apr 17, 2005 · Updated: May 18, 2018 · by CooksInfo. Copyright © 2021 · This post may contain affiliate links · This blog generates income via ads · All-Blue are medium-sized potatoes with smooth, deep blue skin. Their dark blue flesh, almost purple, holds its colour after cooking, unless overcooked. The plant even has blue flowers above ground. These are floury potatoes.